The present invention relates to a direct-coupled rotary damper actuator, and more particularly to a two-position actuator having a DC solenoid element for locking a damper in an open position.
Invensys Environmental Controls manufactures the MA-2XX series direct-coupled rotary damper actuators. Typically, this series of actuators is mounted to an OEM""s smoke and fire air damper to control damper position and thus building air ventilation under normal condition, and to effect a closed damper position whenever desired, e.g., to starve a fire under a fire condition. In the previous design of MA-2XX actuators, when power is applied to the actuator, its output shaft rotates. This rotation drives the damper to the xe2x80x9cpowered position.xe2x80x9d After 90 degrees, plus or minus 3 degrees, of output shaft rotation, a limit switch is activated. This activation switches to a shaded pole motor""s higher impedance holding winding to reduce power consumption and motor noise, and minimize the motor coil temperature rise. The actuator maintains the fully open position of the damper as long as power is applied to the motor holding coil winding. When power is removed, the force created by the damper spring returns the actuator and the damper to a closed position.
In a typical damper application, the actuator maintains the fully open damper position by energizing t he motor holding coil for the period during which the damper is required to be open because the space affected requires ventilation. The actuator returns the damper to the fully closed position by de-energizing the holding coil when the space affected does not require ventilation. In some instances, a space will require ventilation during the day when it is occupied with people, and ventilation can be shut down at nighttime, or during emergency fire conditions, thus allowing the damper to return to the closed position.
It should be noted that a normally open damper application might also occur, with an actuator utilized to close the damper and a motor holding coil energized for the period during which the damper is required to be closed. The actuator then returns the damper to the fully open position by de-energizing the holding coil when the space affected requires ventilation.
Returning to the more c common normally closed application, for special-use, buildings such as hospitals, prisons, hotels, etc., the time in which the space is occupied or requires ventilation can be unlimited, thus requiring the damper to remain in the open position and the holding coil to remain continuously energized. When the holding coil is continuously energized, long term fretting/wear/corrosion may develop on the gear teeth, journal bearing surface, rotor shaft, and gear shafts, due to the micro-motion generated by AC motor coil amplitude. When the actuator is eventually de-energized, the fretting could adversely affect the return operation of the mechanism.
For the foregoing reasons as well as o other disadvantages not specifically mentioned, there is a need for a mechanical interlock mechanism, such as that found in the present invention, to better ensure reliable operation of the damper, and to create an economical, reliable, compact, and energy efficient alternative for damper control.
The present invention is directed to a two-position actuator with a DC solenoid element for locking a damper in an open position. An electric motor assembly is mounted within the actuator. A gear train translates rotary power from the motor assembly, through a series of gears, to an output coupling. A brake rotor is interconnected with, and makes up a portion of, the gear train. A solenoid with one of a selection of activation elements is mounted within the housing in a position to allow the particular activation element to apply a braking force on the brake rotor. This prevents rotation of said brake rotor and the gear train.
Such a result is desirable for connection with a ventilation damper. The actuator is mounted to a damper unit and a damper shaft is removably connected to the output coupling. When the actuator is activated, the motor assembly rotates the output coupling via the gear train, which in turn rotates the damper shaft to a desired damper position. Once the desired position is obtained, the solenoid activation element applies a braking force to the brake rotor and maintains the damper position until otherwise instructed.
This position could be held for an unlimited amount of time, however, the device allows for the solenoid to retract and the damper to fall to a closed position upon power failure. Such power failure may occur during, for example, a fire or smoke condition. The solenoid may also be signaled to retract if for some other reason it is desirable for the damper to close.
In the situation of a normally open damper, a similar arrangement exists. The damper position is adjusted via activation of the actuator. Once the desired position is obtained, the solenoid activation element applies a braking force to the brake rotor and maintains the damper position until otherwise instructed. Upon retraction of the solenoid either by controlled instruction or by power failure, the damper returns to the open position.